I. Field of the Invention
The present invention relates to a fluid system for controlling the movement of a fluid motor and, in particular, the present invention relates to a hydraulic memory unit for a directional control valve.
II. Description of the Prior Art
Heretofore numerous fluid systems have been employed for directing fluid under pressure from a pump to a fluid motor, such as a rotary motor or a cylinder. In the aforementioned U.S. Pat. No. 3,653,208 it was suggested that a pump could be connected in a closed-loop circuit to a fluid motor with the direction of movement of the motor being controlled by a four-way directional control valve incorporated in the circuit between the pump and the motor. In such a system the four-way valve is of the tandem center type; and, thus, in the event of a power failure, springs within the four-way valve automatically center the spool of the valve such that operation of the motor is terminated. Thus, upon reactuation of the system it is not automatically determined what the direction of movement of the motor was prior to the power failure. It would thus be desirable to provide a simple means for modifying conventional directional control valves of the type disclosed herein wherein fluid will be directed to its original path upon reactivation of a system subsequent to a power failure.